The transmitter to the TV uses a circuit that incorporates a 555 timer chip. The signal from the microcontroller is sent to the 555 timer reset input. This controls the output of a 40 kHz signal to an infrared LED. It was found that the existing timer outputs a signal with a frequency of 27kHz – this is not sufficient for controlling a television. A new, improved, circuit will have to be developed.

It was concluded that it would be simpler to create a whole new circuit, with the transmitter and receiver on separate boards.

• Code to decode an IR signal using the SIRC protocol